Efficient and practical synthesis of optically active 5-t-butyldimethylsiloxy-2-cyclohexenone as a convenient chiral 2,5-cyclohexadienone synthon

An efficient and practical method for the preparation of optically active 5-t-butyldimethylsiloxy-2-cyclohexenone (3), a convenient chiral 2,5-cyclohexadienone synthon, from readily available ethyl 4-chloro-3-hydroxy-butyrate (7) has been developed where Ti(II)-mediated intramolecular nucleophilic acyl substitution and FeCl3-mediated ring expansion are the key reactions. The synthesis of racemic 6-t-butyldimethylsiloxy-2-cycloheptenone (10), a potential 2,6-cycloheptadienone synthon, is also described. (C) 1997 Elsevier Science Ltd.